Positive or hormone receptor-unknown breast cancer   Initial hormone therapy depends in part, on the patient’s menopausal status.  For postmenopausal patients with newly diagnosed metastatic disease and estrogen receptor (ER)-positive tumors, progesterone receptor (PR)-positive, or ER/PR-unknown tumors, hormone therapy is generally used as initial treatment.  Hormone therapy is especially indicated if the patient’s disease involves only bone and soft tissue and the patient either has not received adjuvant antiestrogen therapy or has been off such therapy for more than 1 year.  While tamoxifen has been used for many years, several randomized trials suggest equivalent or superior response rates and progression-free survival (PFS) for the AI therapy compared with tamoxifen.

Source:  NCI  2019